Sunday, February 07, 2016

The Third Epidemiological Transition (Revisited)

#10,981

Five years, and more than 5,500 entries ago, I wrote a blog called The Third Epidemiological Transition, based on the works of the late (May 22, 1936 - May 15, 2014) anthropologist and researcher George Armelagos of Emory University.

The gist of his theory is that since the mid-1970s the world has entered into an age of newly emerging infectious diseases, re-emerging diseases and a rise in antimicrobial resistant pathogens.

Since I published that blog we've seen the emergence of MERS-CoV from camels in the Middle East, the emergence of avian H7N9, H5N6, and H10N8 in China (along with a plethora of other avian flu viruses), an unprecedented Ebola outbreak in Western Africa, the largest outbreak ofhuman H5N1 on record (in Egypt), and the sudden and rapid spread of Chikungunya and Zika into the Americas.

All zoonotic infections, and all raising concerns of serious global public health impact.

While the ultimate impact of these emerging infectious diseases remains undetermined, they all remain in play - and as predicted by Dr. Armelagos - seemed destined to be joined by an even greater number of emerging disease threats in the months and years ahead.

With all that in mind, and given the slow news on this Sunday morning, today seemed like an excellent time to revisit Dr. Armelagos' work from my Feb 2011 blog:

While those who embrace new age philosophy will likely insist that this is the dawning of the Age of Aquarius, according to well respected anthropologist and researcher George Armelagos of Emory University, we are actually entering the Third Epidemiological Transition.

This
paper, along with Dr. Greger’s book, made a big impression on me, and
has influenced the direction of AFD over the years. Instead of
remaining avian-flu centric, I’ve endeavored to expand the scope of this
blog to include many other emerging disease threats.

In a nutshell, Armelagos et al. proposed that the history of human disease could be divided into 4 broad eras marked by three major transitions.

(Note:
The evolution of humanity isn’t monolithic or even linear in nature.
There remain societies today that still live a nearly Paleolithic
existence, and others that remain in largely a pre-industrial revolution
age.)

The first era, dubbed the Paleolithic Baseline, depicts the first few million years of human existence, up to about 10,000 years ago.

Mankind
existed in small, isolated groups as hunter-gatherers where population
size and density remained low. Their sparse interaction with humans and
other animals, along with limited range of travel, tended to minimize
the effect of infectious diseases.

While
diseases and parasites plagued humans, those that required a
constant supply of susceptible hosts, tended to die out quickly.

The First Epidemiological Transition
occurred when man moved towards a more agricultural society, about 100
centuries ago. While increasing food security and nutrition, this
transition also introduced several significant disease factors.

In
order to improve the land and make it fertile, mankind became less
nomadic, and settled into larger population clusters. Villages grew
into towns, towns grew into cities.

Pathogens that once might have died out after infecting a single extended family unit, now had ample opportunities to spread.

And by eschewing the nomadic lifestyle, people stayed in one place and increased their contact with human (and animal) waste, and often contaminated their water supplies.

The domestication of animals brought other disease vectors in close contact with humans. Q Fever, Anthrax, and tuberculosis all gained access to human hosts.

And even the cultivation of soil, and the clearing of land, exposed people to insect bites, bacteria, and parasites.

As
cities grew, and exploration of the surrounding world increased, man
spread deadly diseases in ever-greater numbers. Cholera, plague,
influenza, and typhus all became major scourges for humanity.

The SecondEpidemiological Transition began roughly 200 years ago, with the Industrial revolution.

While many of the existing diseases brought forth during the first transition certainly did not go away, new – chronic, non-infectious, degenerative diseases – were added to the mix.

With
advances in medicine, sanitation, and technology the average lifespan
markedly increased. With that came diseases of age that simply hadn’t
been all that common when 40 years was considered a long life (e.g. heart problems, osteoarthritis, cancer).

Technology
also brought with it smokestack industries, chemical toxins, working
indoors as opposed to out, increased stress, and greater access to less
`healthful’ food.

And with this second transition
we’ve seen rises in allergies, asthma, autoimmune disorders, and
sexually transmitted diseases as well.

The Third Epidemiological Transition began in the late 1970s or early 1980s, and is hallmarked by newly emerging infectious diseases, re-emerging diseases carried over from the 2nd transition, and a rise in antimicrobial resistant pathogens.

When you combine those factors with an increasingly mobile global population of about 7 billion people, and huge increases in the number of animals being raised for food consumption (often in environments conducive to the spread of diseases), and you have a recipe for explosive growth in diseases.

In a 2010 paper, Armelagos along with Kristin Harper, updated his original paper. Both papers are well worth reading.

Research
released at conference calls for thinking through the health impacts of
agricultural intensification to control epidemics that are decimating
herds and endangering humans

NEW
DELHI (11 February 2011) – Increasing numbers of domestic livestock and
more resource-intensive production methods are encouraging animal
epidemics around the world, a problem that is particularly acute in
developing countries, where livestock diseases present a growing threat
to the food security of already vulnerable populations, according to new
assessments reported today at the International Conference on
Leveraging Agriculture for Improving Nutrition & Health.(Continue . . . )

These issues aren’t new, of course. In fact, they have been a major component of flublogia since the beginning.

Maryn McKenna addresses them regularly in her blog, particularly in regards to antibiotic abuse and growing antimicrobial resistance on the farm.

Diseases
that might never have evolved fifty or 100 years ago - when Old
McDonald had a half dozen sows on his farm - have a much better
opportunity to spread and mutate when introduced into CAFOs (Concentrated Animal Feeding Operations) with thousands of pigs or hundreds of thousands of chickens.

We
live in an amazingly complex and interconnected world, where what
happens on a chicken farm in China, a pig operation in Belarus, or even
at a cockfight in Indonesia can ultimately impact the health of people
around the world.

Oceans and long distances are no
longer barriers to the spread of diseases. A new virus strain can
literally hop a plane in Beijing, and be in Montreal in less than 24
hours.

And that is exactly what happened in 2003 with SARS.

We
can no longer afford to think of cholera in Haiti, or dengue in Brazil,
or even an outbreak of some new cattle disease in Myanmar as being
someone else’s problem.

In this Third Epidemiological Transition, ailments from even the most remote corners of the globe are fully capable of reaching our shores.

Today,
our best protection is an early warning system that can tell us when a
new disease threat has emerged, or that an old one is gaining momentum.
Only then can we possibly hope to muster resources early enough to
mitigate the threat.

Which is why much more attention must be paid to global surveillance, international cooperation, and the immediate reporting of human and zoonotic disease outbreaks.

The spread of infectious diseases can no longer be constrained by oceans or artificial geopolitical borders.